Method and apparatus for joining two elements made of metal or thermoplastic material

ABSTRACT

A method of joining by friction two elements of metal or thermoplastic material in which the elements are maintained immobile in axially aligned spaced relation and an intermediate member is inserted therebetween for rotational movement while in pressure contact with the ends of the tubular members to be joined and the surfaces are softened by friction after which rotational movement of the intermediate member is stopped while maintaining pressure contact until the weld sets.

United States Patent [1 1 Paolini July 17, 1973 METHOD AND APPARATUS FORJOINING TWO ELEMENTS MADE OF METAL OR THERMOPLASTIC MATERIAL Laurent L.Paolini, Residence Eugenie, 92 St.Cloud, France Filed: May 28, 1971Appl. N0.: 148,090

Inventor:

Foreign Application Priority Data June 5, 1970 France 7020675 US. Cl..-29/470.3, 156/73, 228/2 Int. Cl. 823k 27/00 Field of Search 228/2;29/4703;

References Cited UNITED STATES PATENTS 6/1968 Blum et al. 29/4703Hollander et al. 29/4703 Tramm et al. 228/2 X Primary Examiner-Robert D.Baldwin Assistant Examiner-Robert J. Craig Atl0meyMcDougall, Hesh &Scott 10 Claims, 2 Drawing Figures PATENTED JUL 1 7 ma FIG.

FIG. 2

i l'lllllnl I N VEN TOR.

w W MM u 3 my 5mm R l m 1 METHOD AND APPARATUS FOR JOINING TWO ELEMENTSMADE OF METAL OR THERMOPLASTIC MATERIAL This invention relates to weldedtubular elements,

and it relates more particularly to elements of great length which aresought to be welded one to the other or to various connecting members inwhich the tubular elements are formed of materials such as metal or thermoplastic.

The invention is applicable particularly to the construction of a pipingsystem of large diameter, such as for oil or gas pipe lines orelectrical or communication conduits.

Such pipe systems are currently made of tubular elements which arejoined, as by on site welding. ln order to reduce the number of welds,the tubular elements are generally of substantial length, such as metersor more. The welds are usually made with a welding torch or by arcwelding. The performance of these welding methods often give rise toproblems which are difficult to overcome by reason of the fact that suchmethods are usually carried out manually on site; require the additionof material differing in composition from that of the tubes, and eachweld must be subjected to careful examination.

In order to overcome these difficulties, the proposal has been made thattubular elements be welded together by rotating one element against theremainder of the previously assembled pipe system maintained in a fixedposition. The rotation is carried out under suffiing each other, placingbetween said surfaces an intermediate member such that the end surfacesto be joined are each in contact with the opposite ends of theintermediate member, rotating the intermediate member while bringing theelements to be joined in the direction towards each other until thesurfaces in contact with the rotating member are caused to soften byfriction, continuously adjusting the position of the intermediate memberalong an axis perpendicular to the surfaces to be welded, and finallystopping the rotation of the intermediate member, while maintainingpressure on theparts to be joined, until the weld sets.

The method of the invention is especially applicable to the joinder oftubular elements of considerable length which may be formed of metalsuch as iron, copper, aluminum, or alloys of such metals, or of plasticmaterial such as polyethylene, polyvinyl chloride and the like. Althoughthe method of the invention can be applied to the welding of materialsof different compositions, provided they are compatible with respect tothermal welding, it is of particular interest when the elements to bewelded and the intermediate members are of the same compositions, inwhich event the joining operation enjoys all of the advantages ofautogenous welds.

In one embodiment of the invention, the elements are joined by means ofan intermediate member which simcient pressure to produce frictionbetween the parts to be welded. This friction is continued until thesoftening, due to temperature rise of the parts to be joined, issufficient for the parts to weld together. Rotation of the tubularelement is then terminated while pressure is maintained until the weldhas solidified.

Although this latter method provides an interesting solution forfabricating pipe systems of considerable length, it neverthelesssuffersfrom a number of disadvantages. It requires rotation of thetubular element to be welded, which, because of the length of theelement, involves the use of bulky on site machinery which may bedifl'icult to adapt to uneven surfaces of the ground on which it rests,since this method does not permit tubular members to be properly joinedunless the axes are perfectly aligned. Moreover, rotation of tubularelements of the type described requires a considerable aamount ofenergy. I

It is an object of this invention to provide a method for weldingtubular elements of great lengths which maintain the advantages offriction welding while overcoming the abovementioned disadvantages.

These and other objects and advantages of this invention willhereinafter appear and for purposes of illustration, but not oflimitation, reference is made to the accompanying drawings in which FIG.1 is a schematic elevational view of the appara tus employed in thepractice of this invention; and

FIG. 2 is an elevational view showing the arrangement of parts for thejoinder of tubular elements of considerable length.

Breifly described, the invention comprises a method which makes use offriction for joining two elements of metal or thermoplastic material.The method comprises maintaining the elements substantially'immobilerelative to each other with the surfaces to be joined facply comprises ashort section of a tubular member having the same diameter as thetubular elements and having a thickness which is equal to or greaterthan the thickness of the elements to be joined. This intermediatemember can also be a circular collar or two collars which arepre-assembled by bolting and which are separated by a joinder. In thelatter case, the assembly formed can be dismantled.

The intermediate member is rotated about an axis which, when joiningaligned tubes, is identical with the axis of the tubes. The rotation canbe continuous in one direction or reciprocating. The rotational movementcan be effected simply by mechanical means, such as, for example, adrive rim which is locked onto the intermediate member with the driverim itself being operative mechanically by a gear drive, chain drive,drive belt or other means. The elements to be joined are broughttogether by locking one of the two elements and applying axial force tothe other, such as by means of a ram. The axial force is thustransmitted from the one member to the intermediate member and throughthe intermediate member to the other member to be joined. When joining apipe system of great length, the portion of the pipe system which hasalready been joined together is held in fixed position and the axialforce is applied to the tubular element to be welded onto the previouslyjoined pipe system. It is desirable to be .able to modify the positionof the intermediate member along an axis perpendicular to the surface tobe welded so as to achieve the optimum welding conditions on both endsof the intermediate member. This can be achieved by means of adifferential axial force which can be applied, for example, by means ofa system of additional double acting rams which move the intermediatemember towards or away from the fixed tubular element.

It is important that the elements to be joined be progressively broughttogether in order to avoid tearing of the surfaces of the material to bewelded and in order to reduce the power consumption of the weldingoperation. A preferred method of carrying out the invention comprisesrotating the intermediate member first without applying any axial force.Thereafter, when the intermediate member reaches its normal speed ofrotation, the operation for bringing the elements together is initiated,preferably without the generation of sparks.

When the desired degree of softening is reached, as indicated by theappearance of a small collar of softened material around the surfaces tobe joined, rotation of the intermediate member is terminated but theaxial force is maintained to maintain pressure against the part to bejoined until the weld has solidified.

The complete operation, includingadjusting the position of theintermediate member, is preferably achieved by means of a controlapparatus which is responsive to the temperature and the flow rate ofthe weldings and which acts, for example, on the rams.

The method of this invention is especially adapted to the welding ofpipe systems in a straight line but it can also be used for joiningtubular elements which are arranged at an angle one to the other. Thus,when joining two pipe elements having the shape of cylinders ofrevolution and aligned at an angle to each other, the surfaces to bejoined, which must be parallel, are of elliptical shape. Theintermediate member, which can be a tube portion or a circular collar,is formed with an internal diameter which is at most equal to that ofthe cylinders of revolution, whereas the external diameter of theintermediate member is at least equal to that of the major axis of theellipse.

In such instance, it is possible to rotate the intermediate memberbetween the surfaces to be joined while maintaining contact at allpoints between the surfaces to be joined.

Other embodiments of the method of the invention can also be employed.It is possible, for example, to join two pipe elements of differentdiameters by means of an intermediate member which is of a shape andthickness sufficient to bear against the whole of the surfaces to bejoined together.

The method can also be employed for fixing a pipe to a solid flange, avalve or a T-shaped conduit, for example.

Referring now to the drawings, illustration will be made with referenceto the joinder of elongate steel pipes on the ground. The completejoining apparatus, illustrated in FIG. 1, comprises a driving carriage lsupporting the part 2 of the pipe system which has already been joined,the pipe element 3 to be added, and a tube portion 4 acting as anintermediate member. The pipe element 3 is also carried by the supportcarriage 5 which is connected to the drive carriage l by a reaction bar6. The carriage 5, which has a control device not shown, serves solelyto keep the intermediate pipe element 4 aligned.

The driving carriage, illustrated in detail in FIG. 2, comprises amobile system 7 of wheels and caterpillar tracks which enable thecarriage to be moved over the ground and a mechanical device mounted ona pivot 8. The mechanical device comprises a system for locking theadjacent ends of pipes 2 and 3- in aligned position, such mechanicaldevice being diqgrammatically illustrated as jaws 9 and 10. The pressureon the surfaces to be welded is provided by a ram 11 which connects thejaws 9 and 10. A pivot 12 permits the jaws 9 and to be moved axially inthe direction toward and away from each other.

Fixed to the intermediate member 4, by means of jaws 13, is a drive ring14 having two pulleys l5 and 16 which are rotationally supported onrolling bands 17 and 18 fixed onto a frame 19 which is rigid with thejaws 9 and 10. In this way, the intermediate member 4 is maintained inaxial alignment with the pipe elements 2 and 3 to be joined. Theintermediate member 4 is rotated by way of the drive ring 14 by means ofa conventional motor drive system which is not shown.

A differential axial force can be applied to the intermediate member 4by means of a jack 20 which is fixed on the one hand to the jaw 9 and onthe other hand to the drive ring 14.

The operation of joining pipe elements by means of the above describeddevice takes place in the following manner:

The end of the pipe system 2, which has already been joined, is fixed tothe driving carriage l by means of the clamping jaws 9. The intermediatemember 4 is also positioned in axial alignment with the end of the pipeelement 2 with the ring 14 mounted thereon. One end of the pipe element3 is also engaged into the driving carriage 1 while a distant end of thepipe element 13 is supported by the carriage 5. While the pipe elements2 and 3 are locked in fixed position in axial alignment by the jaws 9and 10, the intermediate member is rotated. The tubular element 3 isdisplaced in the direction towards the tubular element 2 by means of aforce supplied by the ram 11 until the surfaces to be joined are broughtinto pressure contact one with the other with the intermediate member 4therebetween. While rotating, the position of the intermediate member iscontinuously adjusted, as by means of the ram 20, in order to achieveuniform welding conditions on both ends of the member 4. By reason ofthe frictional engagement between the rotating intermediate member 4 andthe frictionally engaged ends of the tubular ends 2 and 3, thetemperature rises sufficient to cause softening of the metal. When abead is formed, indicating that sufficient of the metal has beensoftened, rotation of the intermediate member is stopped while thepressure is maintained by means of the ram 11 until the weld has set.

The above described operations are directed by means of a controlapparatus responsive to data re ceived from: two gauges of the type usedfor measuring metal flow, which gauges measure the speed of the flow ofthe metal in the welding zones; two optical pyrometers which measure thetemperature of the zones of the weld.

The measuring instruments are connected to a control apparatus by meansof a wheatstone bridge wiring system which provides the controlapparatus, with the physical data compared in pairs. From these data,the control apparatus continuously determines the position to which theintermediate member 4 should be adjusted in relation to the pipeelements 2 and 3. If necessary, it operates the rams of the piston andcylinder devices 20 and 11, as well as the motor drive for the ring 14.

It will be apparent from the foregoing that the invention describedaffords many advantages over methods which have previously beenemployed. It becomes possible rapidly to produce welds of high quality,without the need for highly skilled labor. Since the method isrepetitive, the different welds made along the same piece of pipe areidentical and, for this reason, there is no need systematically toexamine each of the welds.

The method also makes it possible to join pipe elements which arealigned or arranged at an angular relationship one to the other, even onuneven surfaces. It can be used for welding pipes together with otherelements, such as collars or valves. Finally, the apparatus is smallerand consumes less energysince only a short, light weight, intermediatemember of small energy is adapted to be rotated.

It will be understood that changes may be made in the details ofconstruction, arrangement and operation without departing from thespirit of the invention, especially as defined in the following claims.

Iclaim:

l. A method for joining two elements of metal or thermoplastic materialcomprising maintaining the elements substantially immobile relative toeach other with the surfaces to be joined facing each other in spacedparallel plane, positioning an intermediate member between the surfacesto be joined, rotating the intermediate member while in pressure contactwith the surfaces to be joined until the said surfaces are caused tosoften by friction, adjusting the position of the intermediate member ina direction perpendicular to the surfaces to be welded during rotationalmovement of the intermediate member in response to temperature and flowat the welding zone to provide uniformity in the welds at both ends ofthe intermediate member, and stopping rotation of the intermediatemember while maintaining axial pressure on the parts to be joined untila weld has solidified.

2. A method as claimed in Claim 1 which includes the step of axiallydisplacing at least one of the elements in tion about the axis of theelements to be joined.

5. A method as claimed in claim 1 in which the intermediate member isrotated in a reciprocal movement about the axis of the elements to bejoined.

6. A method as claimed in claim 1 which includes the steps ofcontrolling the position of the intermediate member in response totemperature and flow at the welding zone.

7. A method as claimed in claim 1 in which the elements to be joined andthe intermediate member are formed of a material selected from the groupconsisting of a metal in the form of iron, copper, aluminum and alloysthereof, and a thermoplastic material in the form of a polyethylene andpolyvinyl chloride.

8. An apparatus for joining two tubular elements by friction comprisingsupport means for maintaining the ends of the tubular elements in fixedposition in parallel spaced relation, means for supporting a shorttubular member in alignment between the spaced ends of the tubularelements, means for rotating the short tubular member between thetubular elements to be joined, traction means for moving at least one ofthe tubular elements in the direction towards the other to effectpressure contact between the end surfaces of the tubular elements andthe tubular member during rotational movement to soften the material byfrictional engagement, sajd traction means being effective to maintainaxial pressure after the material has been reduced to a softened stateand the rotational movement of the tubular member has been stopped toeffect joinder, and means for adjusting the position of the tubularmember relative to the ends of the tubular elements in response totemperature and flow at the weld zones.

9. An apparatus as claimed in claim 8 in which the tubular member ismounted for continuous movement in one direction.

10. An apparatus as claimed in claim 8 in which the tubular member'ismounted for reciprocal movement.

1. A method for joining two elements of metal or thermoplastic materialcomprising maintaining the elements substantially immobile relative toeach other with the surfaces to be joined facing each other in spacedparallel plane, positioning an intermediate member between the surfacesto be joined, rotating the intermediate member while in pressure contactwith the surfaces to be joined until the said surfaces are caused tosoften by friction, adjusting the position of the intermediate member ina direction perpendicular to the surfaces to be welded during rotationalmovement of the intermediate member in response to temperature and flowat the welding zone to provide uniformity in the welds at both ends ofthe intermediate member, and stopping rotation of the intermediatemember while maintainiNg axial pressure on the parts to be joined untila weld has solidified.
 2. A method as claimed in Claim 1 which includesthe step of axially displacing at least one of the elements in thedirection towards the other to maintain pressure contact between thesurfaces.
 3. A method as claimed in claim 1 in which the elements to bejoined are of tubular shape and wherein the intermediate member is atubular member of short length.
 4. A method as claimed in claim 1 inwhich the intermediate member is continuously rotated in one directionabout the axis of the elements to be joined.
 5. A method as claimed inclaim 1 in which the intermediate member is rotated in a reciprocalmovement about the axis of the elements to be joined.
 6. A method asclaimed in claim 1 which includes the steps of controlling the positionof the intermediate member in response to temperature and flow at thewelding zone.
 7. A method as claimed in claim 1 in which the elements tobe joined and the intermediate member are formed of a material selectedfrom the group consisting of a metal in the form of iron, copper,aluminum and alloys thereof, and a thermoplastic material in the form ofa polyethylene and polyvinyl chloride.
 8. An apparatus for joining twotubular elements by friction comprising support means for maintainingthe ends of the tubular elements in fixed position in parallel spacedrelation, means for supporting a short tubular member in alignmentbetween the spaced ends of the tubular elements, means for rotating theshort tubular member between the tubular elements to be joined, tractionmeans for moving at least one of the tubular elements in the directiontowards the other to effect pressure contact between the end surfaces ofthe tubular elements and the tubular member during rotational movementto soften the material by frictional engagement, said traction meansbeing effective to maintain axial pressure after the material has beenreduced to a softened state and the rotational movement of the tubularmember has been stopped to effect joinder, and means for adjusting theposition of the tubular member relative to the ends of the tubularelements in response to temperature and flow at the weld zones.
 9. Anapparatus as claimed in claim 8 in which the tubular member is mountedfor continuous movement in one direction.
 10. An apparatus as claimed inclaim 8 in which the tubular member is mounted for reciprocal movement.